Typically, while transferring a document, an image reading apparatus such as a scanner captures an image of the document, using an image capturing device such as a line sensor with imaging elements arranged one-dimensionally. For this reason, a foreign object such as paper powder, dust and paste, etc., attached to a glass surface of the image capturing device may cause vertical stripe noise to appear on a document image acquired by capturing the document.
A printer system that reads a white reference plate and a blank region of a print document, discriminates whether the white reference plate or contact glass is a source of detected dirt, based on the obtained dirt detection result, and displays a position of the dirt and a cleaning instruction is disclosed (see patent literature 1).